1. Field of the Invention
This invention relates to air circulation devices, and more particularly, to a method and apparatus for circulating air.
2. Description of the Related Art
In various industries such as those involving agriculture and manufacturing, it is often necessary to circulate relatively large amounts of air through a building. In such circumstances, a fan is often installed in the wall of the building to assist in the circulation of air. Such fans typically have a housing which extends at least partially through the wall of the building as well as a plurality of blades which rotate within the housing.
The housing of such a fan generally has an annular wall which is disposed adjacent to the end portions of the blades of the fan. The annular wall serves to define the flow path for air circulating through the housing. As will be appreciated by those skilled in the art, it is desirable to have the distance between the end portions of the fan blades and the annular wall of the housing be as small as possible so as to improve the efficiency of the fan. However, to minimize this distance, it is often necessary that the annular wall be relatively rigid so as not to deform and contact the blades during operation of the fan. This typically requires that the material forming the housing be relatively rigid. In addition, the hub assembly to which the blades are secured has to be carefully positioned within the housing to ensure that the blades do not contact the annular wall of the housing during movement. This generally requires that the mounting member, which is used to support the hub assembly and the motor, be carefully oriented in the housing. Since the mounting member typically includes a number of brackets which are secured to the housing by fasteners, it is often necessary to precisely position the brackets and fasteners to ensure that the blades of the fan are centered within the housing.
In addition to the foregoing, some fans which are used to circulate air through buildings use a belt drive mechanism. In such circumstances, the fan includes a rotating shaft which is attached to both the fan hub assembly as well as to a first pulley. The first pulley in turn is connected to a second pulley by means of a V-belt. Because the second pulley is driven by a motor, the V-belt causes the first pulley to rotate which in turn causes the blades of the fan to rotate.
While this particular type of fan design is effective, there are nevertheless certain disadvantages associated with this design. For example, relatively expensive pillow block bearings (or similar) have to be used to permit rotation of the shaft which is used to drive the fan hub assembly. In addition, the bearings, the first pulley, as well as the hub assembly often tend to rust and become secured to the shaft. It therefore becomes difficult to disassemble the hub assembly as well as the first pulley from the shaft to service these particular components. In addition, the first pulley is typically formed by machining a casting which tends to make the first pulley more expensive than pulleys which are formed by other procedures such as by sheet metal stampings.